I. Field of the Invention
The present invention relates to mobile telephony. More particularly, the present invention relates to a novel and improved method and apparatus for providing roaming indication indicative of anticipated roaming charges.
II. Description of the Related Art
As mobile communication systems become more prevalent in society the demands for greater and more sophisticated service have grown. To meet the capacity needs of mobile communication systems, techniques of multiple access to a limited communication resource have been developed. The use of code division multiple access (CDMA) modulation techniques is one of several techniques for facilitating communications in which a large number of system users are present. Other multiple access communication system techniques, such as time division multiple access (TDMA) and frequency division multiple access (FDMA) are known in the art. However, the spread spectrum modulation technique of CDMA has significant advantages over these modulation techniques for multiple access communication systems.
The use of CDMA techniques in a multiple access communication system is disclosed in U.S. Pat. No. 4,901,307, issued Feb. 13, 1990, entitled "SPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS", assigned to the assignee of the present invention, of which the disclosure thereof is incorporated by reference herein. The use of CDMA techniques in a multiple access communication system is further disclosed in U.S. Pat. No. 5,103,459, issued Apr. 7, 1992, entitled "SYSTEM AND METHOD FOR GENERATING SIGNAL WAVEFORMS IN A CDMA CELLULAR TELEPHONE SYSTEM", assigned to the assignee of the present invention, of which the disclosure thereof is incorporated by reference herein.
Users of mobile telephones have desired to be able to use their mobile phone regardless of their location This desire caused mobile communications providers to negotiate contracts among themselves to provide services known as "roaming" to their customers. A "roamer" is a mobile station which requires service in a system which is operated by a mobile communications service provider other than the one to which the user subscribes.
Currently when a mobile station is roaming, a signal indicative of the roaming condition is provided to the user and displayed as a result of a comparison of the system identification (SID) of the subscribed system which is semi-permanently stored in the mobile station with the SID of the system providing service broadcast from the base station. This alerts the user of the mobile station that the service being provided is accruing roaming costs. Because the contracts between different companies differ, a roamer is typically assuming an unknown risk as to the cost of the service being provided, since he knows neither of the contracts between the service provider and system to which he subscribes nor does he know the identity of the provider of the roaming service.